The current of Galileo’s life had hitherto flowed in a smooth and unobstructed channel. He had now attained the highest objects of earthly ambition. His discoveries had placed him at the head of the great men of the age; he possessed a professional income far beyond his wants, and even beyond his anticipations; and, what is still dearer to a philosopher, he enjoyed the most perfect leisure for carrying on and completing his discoveries. The opposition which these discoveries encountered, was to him more a subject for triumph than for sorrow. Prejudice and ignorance were his only enemies; and if they succeeded for a while in harassing his march, it was only to lay a foundation for fresh achievements. He who contends for truths which he has himself been permitted to discover, may well sustain the conflict in which presumption and error are destined to fall. The public tribunal may neither be sufficiently pure nor enlightened to decide upon the issue; but he can appeal to posterity, and reckon with confidence on “its sure decree.”

The ardour of Galileo’s mind, the keenness of his temper, his clear perception of truth, and his inextinguishable love of it, combined to exasperate and prolong the hostility of his enemies. When argument failed to enlighten their judgment, and reason to dispel their prejudices, he wielded against them his powerful weapons of ridicule and sarcasm; and in this unrelenting warfare, he seems to have forgotten that Providence had withheld from his enemies those very gifts which he had so liberally received. He who is allowed to take the start of his species, and to penetrate the veil which conceals from common minds the mysteries of nature, must not expect that the world will be patiently dragged at the chariot wheels of his philosophy. Mind has its inertia as well as matter; and its progress to truth can only be insured by the gradual and patient removal of the obstructions which surround it.

The boldness—may we not say the recklessness—with which Galileo insisted upon making proselytes of his enemies, served but to alienate them from the truth. Errors thus assailed speedily entrench themselves in general feelings, and become embalmed in the virulence of the passions. The various classes of his opponents marshalled themselves for their mutual defence. The Aristotelian professors, the temporising Jesuits, the political churchmen, and that timid but respectable body who at all times dread innovation, whether it be in religion or in science, entered into an alliance against the philosophical tyrant who threatened them with the penalties of knowledge.

The party of Galileo, though weak in numbers, was not without power and influence. He had trained around him a devoted band, who idolised his genius and cherished his doctrines. His pupils had been appointed to several of the principal professorships in Italy. The enemies of religion were on this occasion united with the Christian philosopher; and there were, even in these days, many princes and nobles who had felt the inconvenience of ecclesiastical jurisdiction, and who secretly abetted Galileo in his crusade against established errors.

Although these two parties had been long dreading each others power, and reconnoitring each others position, yet we cannot exactly determine which of them hoisted the first signal for war. The church party, particularly its highest dignitaries, were certainly disposed to rest on the defensive. Flanked on one side by the logic of the schools, and on the other by the popular interpretation of Scripture, and backed by the strong arm of the civil power, they were not disposed to interfere with the prosecution of science, however much they may have dreaded its influence. The philosophers, on the contrary, united the zeal of innovators with that firmness of purpose which truth alone can inspire. Victorious in every contest, they were flushed with success, and they panted for a struggle in which they knew they must triumph.

In this state of warlike preparation Galileo addressed a letter, in 1613, to his friend and pupil, the Abbé Castelli, the object of which was to prove that the Scriptures were not intended to teach us science and philosophy. Hence he inferred, that the language employed in the sacred volume in reference to such subjects should be interpreted only in its common acceptation; and that it was in reality as difficult to reconcile the Ptolemaic as the Copernican system to the expressions which occur in the Bible.

A demonstration was about this time made by the opposite party, in the person of Caccini, a Dominican friar, who made a personal attack upon Galileo from the pulpit. This violent ecclesiastic ridiculed the astronomer and his followers, by addressing them sarcastically in the sacred language of Scripture—“Ye men of Galilee, why stand ye here looking up into heaven?” But this species of warfare was disapproved of even by the church; and Luigi Maraffi, the general of the Dominicans, not only apologised to Galileo, who had transmitted to him a formal complaint against Caccini, but expressed the acuteness of his own feelings on being implicated in the “brutal conduct of thirty or forty thousand monks.”

From the character of Caccini, and the part which he afterwards played in the persecution of Galileo, we can scarcely avoid the opinion that his attack from the pulpit was intended as a snare for the unwary philosopher. It roused Galileo from his wonted caution; and stimulated, no doubt, by the nature of the answer which he received from Maraffi, he published a long letter of seventy pages, defending and illustrating his former views respecting the influence of scriptural language on the two contending systems. As if to give the impress of royal authority to this new appeal, he addressed it to Christian, Grand Duchess of Tuscany, the mother of Cosmo; and in this form it seems to have excited a new interest, as if it had expressed the opinion of the grand ducal family. These external circumstances gave additional weight to the powerful and unanswerable reasoning which this letter contains; and it was scarcely possible that any man, possessed of a sound mind, and willing to learn the truth, should refuse his assent to the judicious views of our author. He expresses his belief that the Scriptures were designed to instruct mankind respecting their salvation, and that the faculties of our minds were given us for the purpose of investigating the phenomena of nature. He considers Scripture and nature as proceeding from the same divine author, and, therefore, incapable of speaking a different language; and he points out the absurdity of supposing that professors of astronomy will shut their eyes to the phenomena which they discover in the heavens, or will refuse to believe those deductions of reason which appeal to their judgment with all the power of demonstration. He supports these views by quotations from the ancient fathers; and he refers to the dedication of Copernicus’s own work to the Roman Pontiff, Paul III., as a proof that the Pope himself did not regard the new system of the world as hostile to the sacred writings. Copernicus, on the contrary, tells his Holiness, that the reason of inscribing to him his new system was, that the authority of the Pontiff might put to silence the calumnies of some individuals, who attacked it by arguments drawn from passages of Scripture twisted for their own purpose.

It was in vain to meet such reasoning by any other weapons than those of the civil power. The enemies of Galileo saw that they must either crush the dangerous innovation, or allow it the fullest scope; and they determined upon an appeal to the inquisition. Lorini, a monk of the Dominican order, had already denounced to this body Galileo’s letter to Castelli; and Caccini, bribed by the mastership of the convent of St Mary of Minerva, was invited to settle at Rome for the purpose of embodying the evidence against Galileo.

Though these plans had been carried on in secret, yet Galileo’s suspicions were excited; and he obtained leave from Cosmo to go to Rome about the end of 1615.[29] Here he was lodged in the palace of the Grand Duke’s ambassador, and kept up a constant correspondence with the family of his patron at Florence; but, in the midst of this external splendour, he was summoned before the inquisition to answer for the heretical doctrines which he had published. He was charged with maintaining the motion of the earth, and the stability of the sun—with teaching this doctrine to his pupils—with corresponding on the subject with several German mathematicians—and with having published it, and attempted to reconcile it to Scripture, in his letters to Mark Velser in 1612. The inquisition assembled to consider these charges on the 25th of February 1615; and it was decreed that Galileo should be enjoined by Cardinal Bellarmine to renounce the obnoxious doctrines, and to pledge himself that he would neither teach, defend, nor publish them in future. In the event of his refusing to acquiesce in this sentence, it was decreed that he should be thrown into prison. Galileo did not hesitate to yield to this injunction. On the day following, the 26th of February, he appeared before Cardinal Bellarmine, to renounce his heretical opinions; and, having declared that he abandoned the doctrine of the earth’s motion, and would neither defend nor teach it, in his conversation or in his writings, he was dismissed from the bar of the inquisition.